Editing Oxidation state (section)

==== The algorithm's caveat ====
The algorithm contains a caveat, which concerns rare cases of [[transition-metal]] [[coordination complex|complexes]] with a type of [[ligand]] that is reversibly bonded as a [[Lewis acid]] (as an acceptor of the electron pair from the transition metal); termed a "Z-type" ligand in Green's [[covalent bond classification method]]. The caveat originates from the simplifying use of electronegativity instead of the [[molecular orbital|MO]]-based electron allegiance to decide the ionic sign.<ref name="10.1515/pac-2015-1204" /> One early example is the {{chem2|O2S\sRhCl(CO)([[triphenylphosphine|PPh3]])2}} complex<ref>{{cite journal|first1=K. W.|last1=Muir|first2=J. A.|last2=Ibers|title=The structure of chlorocarbonyl(sulfur dioxide)bis(triphenylphosphine)rhodium, (RhCl(CO)(SO2)(P(C6H5)3 2)|journal=Inorg. Chem.|volume=8|date=1969|issue=9|pages=1921–1928|doi=10.1021/ic50079a024}}</ref> with [[sulfur dioxide]] ({{chem2|SO2}}) as the reversibly-bonded acceptor ligand (released upon heating). The Rh−S bond is therefore extrapolated ionic against Allen electronegativities of [[rhodium]] and sulfur, yielding oxidation state +1 for rhodium:

:[[File:8oxstate.svg|frameless|450px]]